Afraid I don't know, my alts were 525 when they were questing in pandaria. If you have quested through the whole of jade forest and not gotten 1 and are below 525, that may be your answer as they seem to show up pretty often if you are eligible for the drop.

you can get the patterns at 500-525 my alt was getting the patterns when his jc was only leveled to the point of cata's jc gems, how ever I have noticed a dramatic nerf to their drop rate compared to getting nearly all the meta patterns in jade forest upon releasee. My 4th jc is 88 and only has a few of the meta's via questing.